A lot of the early "hazmat" regulations were written by the AAR "Bureau of Explosives" (BOE). The early regs had a lot fewer categories of materials because there were a lot fewer hazardous materials. In the pre- depression era some rules book just required explosive or flammable loads to be not next to the engine, caboose, or car with an open flame and as near to the middle of the train as possible. In the 1960's, with the explosion of number of flammable gas shipments (no pun intended), the hazmat regs started to get more complicated and by the 1980's had gone from a half a page to a couple pages in the timetable with a chart. By the 1990's it was multiple pages to a separate pamphlet with two full color charts.
Dave H. Painted side goes up. My website : wnbranch.com
Just to amplify what Dave has explained, a unit train is a train of freight cars that operates as a single unit. 50 bathtub gondolas go from a power plant in Wisconsin to the Powder River Basin, are loaded with coal, and the same 50 cars return to Wisconsin to be unloaded at the power plant. Then the same 50 cars are sent back to the Powder River Basin to get more coal. The cars are never uncoupled or switched generally, they are loaded and unloaded on balloon tracks (kinda like big reverse loops). That's very different from say steam era reefer trains, where the train may run on a schedule every day or every other day or whatever, with roughly the same number of cars, but each train has a different assortment of reefers, not the same exact ones in each train.
Back to the original question re buffer cars. The rules about not having a car with flammable materials in it next to the engine(s) goes back to the days of wood freight cars and steam engines, so has been around for a very long time. Since modern unit tank trains often have engines at both ends of the trains, most railroads just put a buffer car on each end of the tank cars. It's easier to leave both buffer cars there, rather than worrying about removing one if you don't have a helper on the rear, or having to add one if you do.
Coal trains tended to based on what the utility (or mine could handle) size of unloading loop or recieving tracks. As trains got heavier, they were also sold based on what the trains could pull.
Part of it is things change and it depends.
When unit grain trains first started they were marketed in 25 car increments because most grain trains were in the 75 -100 car range. The longer and odd sized trains came later. Train size was limited by weight, because (CSXT definitionnot withstanding), many cars didn't have high strength drawbars. Fast forward 40 years and most 100 ton cars have high strength drawbars, so virtually every car in a unit train is one equipped with high strength drawbars and train length/tonnage is not the issue it once was. 40 years ago conductors carrried a waybill for every car in the train. Fast forward to now and waybills are all virtual, nobody carries a paper document, its just a record in a table with a couple hundred million rows.
dehusman In the early days of the "unit train" concept, they sold units typically in increments of 25 cars, by the late 1980's most of the small units were no longer offered and it was done in train sized increments (75-100-110 cars, up to 125-135 cars in the 1990's). Some of the 25 car units still hung around, the UP had a 25 car coal unit that was added to the point of another unit coal train and was set out and picked up at a cement plant outside Kansas City.
In the early days of the "unit train" concept, they sold units typically in increments of 25 cars, by the late 1980's most of the small units were no longer offered and it was done in train sized increments (75-100-110 cars, up to 125-135 cars in the 1990's). Some of the 25 car units still hung around, the UP had a 25 car coal unit that was added to the point of another unit coal train and was set out and picked up at a cement plant outside Kansas City.
From everything I've read, most of the unit trains D&RGW hauled were based on coal mine demands and tonnage per train cycle. Those unit trains didn't seem to have increments like you listed but might be 105 cars or some other number based on how many cars could carry the volume needed for the plant with so many trips per week.
Rio Grande. The Action Road - Focus 1977-1983
dehusman j. c. according to defenition a unit train is a block of cars carring one product from point a to point b Actually its more than that. A unit is a group of cars travelling on a single waybill. One waybill, many cars. A unit train is a train that carries cars or groups of cars traveling as a unit. A unit grain train is one commodity and it goes from one origin to one destination. But it is a unit train because all 100 cars on the train are traveling on the same waybill. Its one unique waybill with 100 cars listed on it, each of the 100 cars shares the same waybill number. A stack train is one commodity (intermodal) and it goes from one origin to one destination. But it is not a unit train because each container is traveling on a separate waybill. A grain train from the 1950's might be one commodity and might be going from one origin to one destination. But its not a unit train because each car has its own waybill, 100 waybills with one unique car number and one unique waybill number on each. The difference betweeen a unit coal train and coal train is how the cars are billed. Prior to the 1960's there were solid one commodity trains, but they weren't unit trains. It wasn't until the railroads were allowed to cut rates on units in the 1960's that true unit trains happened.
j. c. according to defenition a unit train is a block of cars carring one product from point a to point b
Actually its more than that. A unit is a group of cars travelling on a single waybill. One waybill, many cars. A unit train is a train that carries cars or groups of cars traveling as a unit.
A unit grain train is one commodity and it goes from one origin to one destination. But it is a unit train because all 100 cars on the train are traveling on the same waybill. Its one unique waybill with 100 cars listed on it, each of the 100 cars shares the same waybill number.
A stack train is one commodity (intermodal) and it goes from one origin to one destination. But it is not a unit train because each container is traveling on a separate waybill.
A grain train from the 1950's might be one commodity and might be going from one origin to one destination. But its not a unit train because each car has its own waybill, 100 waybills with one unique car number and one unique waybill number on each.
The difference betweeen a unit coal train and coal train is how the cars are billed. Prior to the 1960's there were solid one commodity trains, but they weren't unit trains. It wasn't until the railroads were allowed to cut rates on units in the 1960's that true unit trains happened.
well not all railroads agree with your definition click on link and scroll down to unit train and see whart CSX says. https://www.csx.com/index.cfm/about-us/company-overview/railroad-dictionary/?i=U
dehusman It had to do with the cars unfortunately having truck centers close to 39 ft (the car was designed to hold a certain capacity and unfortunately that just happened to be the length). On jointed rail, on one side, both trucks hit a joint at the same time amplifying the rocking.
It had to do with the cars unfortunately having truck centers close to 39 ft (the car was designed to hold a certain capacity and unfortunately that just happened to be the length). On jointed rail, on one side, both trucks hit a joint at the same time amplifying the rocking.
I think it might be a bit more than that. I think it likely that it works with ALTERNATING track joints, 19 1/2 feet apart. One joint prompts a car to roll a smidge. Then about 20 feet later, a joint on the other side does it's job. This would prompt a rocking back and forth.
Ed
riogrande5761They did travel in blocks, typically at the front of the train
riogrande5761 so engineers could monitor them as they had the ability at certain speeds to develop a harmonic action causing them to eventually rock them selves off the rails if allowed.
joe323So a modern unit train of say 100 cars carrying the same commodity say vegetable oil from the plant a to plant b is treated the same as a single car carrying the commodity for billing purposes?
Each car would be listed on one waybill, one waybill per unit. You can print a waybill for each individual car, it will just have the same waybill number on it. The practical way the train is handled, the one waybill is transparent to the crews and operating folks.
Here is a little more info regarding unit trains:
Kaiser Unit Coal Trains During mid 1968, UP negotiated an agreement, along with D&RGW and AT&SF, with Kaiser Steel to operate what was to be one of the nation's first unit coal trains, a service involving a dedicated set of new equipment and motive power. The service was planned to bring metallurgical quality coal from mines at Sunnyside, Utah, and the Carbondale, Colorado, to the Kaiser Steel mill in Fontana, California. 1968In 1968 D&RGW and UP began operation of a unit coal train between Sunnyside, Utah, and the Kaiser steel mill in Fontana, California. The train used dedicated full trains of high-sided gondola cars that were loaded at Sunnyside and unloaded at Fontana. The trains also used dedicated sets of SD45 locomotives from both Union Pacific (12 locomotives) and D&RGW (six locomotives).
Kaiser Unit Coal Trains
During mid 1968, UP negotiated an agreement, along with D&RGW and AT&SF, with Kaiser Steel to operate what was to be one of the nation's first unit coal trains, a service involving a dedicated set of new equipment and motive power. The service was planned to bring metallurgical quality coal from mines at Sunnyside, Utah, and the Carbondale, Colorado, to the Kaiser Steel mill in Fontana, California.
1968In 1968 D&RGW and UP began operation of a unit coal train between Sunnyside, Utah, and the Kaiser steel mill in Fontana, California. The train used dedicated full trains of high-sided gondola cars that were loaded at Sunnyside and unloaded at Fontana. The trains also used dedicated sets of SD45 locomotives from both Union Pacific (12 locomotives) and D&RGW (six locomotives).
http://utahrails.net/utahcoal/kaiser-trains.php
Cargill grain cars were regulars thru the Rockies but not as described in the link provided earlier. They did travel in blocks, typically at the front of the train so engineers could monitor them as they had the ability at certain speeds to develop a harmonic action causing them to eventually rock them selves off the rails if allowed. Engineers typically had to either stay below that speed or above it (from memory about 12 to 20 mph) to avoid that situation.
So a modern unit train of say 100 cars carrying the same commodity say vegetable oil from the plant a to plant b is treated the same as a single car carrying the commodity for billing purposes?
Joe Staten Island West
j. c.according to defenition a unit train is a block of cars carring one product from point a to point b
according to defenition a unit train is a block of cars carring one product from point a to point b , so the concept of unit trains can go back to trains of solid stock cars or silk trains and solid trains of refers , but later would include trains of tankcars carring crude get a copy of the book " Decade of the trains the 1940s" , there are pictures of yards with nothing but tank cars . also i belive that the years of ww2 ordance was carried in solid trains.
During the 50's and 60's there wouldn't be tank car "unit trains". There might be solid trains of tank cars, but they wouldn't be unit trains. The tank car trains in the 50's and 60's probably wouldn't be flammable liquids, probably more combustible so wouldn't need cover even if there were hazmat rules.
in 50's and 60's buffer cars were not required .
The question isn't really about unit trains, but the handling of hazardous materials. When the requirements for, and placement of, buffer cars took effect. How those requirements may have evolved over time.
Jeff
Part B of the question is: "When did unit trains come into use?"
Answering my own question Cargill, 1966 http://150.cargill.com/150/en/GRAIN-BY-RAILWAY-TRANSPORT.jsp
Henry
COB Potomac & Northern
Shenandoah Valley
I know modern day tank car unit trains have a buffer car between the loco and tank cars. During the 1950's and 60's was the same policy used or is this something more recent. Thanks.
Bruce